The parathyroid glands are four tiny glands, located in the neck, that control the body’s calcium levels. Each gland is about the size of a grain of rice (weighs approximately 30 milligrams and is 3-4 millimeters in diameter). The parathyroids produce a hormone called parathyroid hormone (PTH). PTH raises the blood calcium level by:
- breaking down the bone (where most of the body’s calcium is stored) and causing calcium release
- increasing the body’s ability to absorb calcium from food
- increasing the kidney’s ability to hold on to calcium that would otherwise be lost in the urine.
Normal parathyroid glands work like the thermostat in your home to keep blood calcium levels in a very tightly controlled range. When the blood calcium level is too low, PTH is released to bring the calcium level back up to normal. When the calcium level is normal or gets a little too high, normal parathyroids will stop releasing PTH. Proper calcium balance is crucial to the normal functioning of the heart, nervous system, kidneys, and bones.
Primary hyperparathyroidism causes abnormally high blood calcium levels mainly be “stealing” calcium from the bones. Every cell and organ in the body uses calcium as a signal to regulate their normal function. Therefore, it is crucial that calcium levels are tightly controlled. Abnormally high blood calcium levels can damage every organ in the body gradually over time. In the past, generations of doctors learned the classic symptoms of primary hyperparathyroidism through the saying “bones, stones, and groans” which represented weakened bones, kidney stones, and abdominal pain. In addition, many patients also had “psychic moans and fatigue overtones” which indicated mood disturbances and fatigue. In extreme cases of severe elevations of blood calcium levels called “hypercalcemic crisis,” patients may present in comatose or near-comatose states with organ failure. However, today most patients are diagnosed through routine blood testing or screening for osteoporosis and many patients have only vague, non-specific symptoms.
Primary hyperparathyroidism is diagnosed through blood tests. Since the parathyroid hormone (PTH) levels control the calcium levels, the two levels normally move in opposite directions. For example, when the blood calcium level is high, the PTH level should be low or on the lower end of normal. When the blood calcium level is low, the PTH level should increase (in order to tell the body to absorb more calcium). In primary hyperparathyroidism, both levels are elevated. Ocasionally in patients with primary hyperparathyroidism, one or both of these levels may be normal, but in the higher end of normal (see Special Cases: Normocalcemic Hyperparathyroidism). Additional tests that may be helpful in making the diagnosis of primary hyperparathyroidism include the blood phosphate level, the vitamin D level, urine calcium levels (a urine test of calcium collected over a 24-hour period), and the blood creatinine level (a measure of kidney function). The 24 hour urine calcium level will help determine if the individual has familial hypocalciuric hypercalcemia (a benign condition not requiring surgery). Vitamin D levels should be checked because low vitamin D levels may be causing a problem called secondary hyperparathyroidism and vitamin D levels need to be cautiously replaced before further work up is done. Patients with elevated calcium and/or parathyroid hormone levels should also have their bone density tested. This is done by a special x-ray test called a DEXA-scan.
Untreated primary hyperparathyroidism can cause a number of health problems over the long term, such as kidney stones and osteoporosis (thinning or weakening of the bones), but most often does not lead to medical emergencies. Once you have been diagnosed with primary hyperparathyroidism, the decision for treatment should be made after careful consideration with the advice of your primary care physician, endocrinologist, and/or endocrine surgeon. Prior to an operation, a series of “localizing tests” (radiology tests to determine which gland(s) are abnormal) will likely be ordered.
Surgical removal, or parathyroidectomy, is the only known cure for primary hyperparathyroidism and is currently the best treatment. In the hands of an experienced endocrine surgeon, success (cure) rates approach 95-98%. Medications such as estrogen and bisphosphonates will NOT cure primary hyperparathyroidism but may decrease calcium or parathyroid hormone (PTH) levels and improve bone density. A new type of medication called calcimimetics (i.e. Sensipar, Cinacalcet) may lower blood calcium levels and PTH levels, but they are not currently approved by the FDA (Food and Drug Administration) for use in primary hyperparathyroidism and will NOT cure the disease. These medications have not been studied to determine whether or not they help decrease effects on other systems in the body or whether they improve the more subjective symptoms of primary hyperparathyroidism (depression, fatigue, muscle aches and pains, difficulty concentrating, memory problems, insomnia, constipation).